The Saginaw River is a 22.4-mile-long (36.0 km) river in the U.S. state of Michigan. It is formed by the confluence of the Tittabawassee and Shiawassee rivers southwest of Saginaw. It flows northward into the Saginaw Bay of Lake Huron, passing through the cities of Saginaw and Bay City, both of which developed around it in the 19th century. The watershed area is 8,595 square miles (22,260 km2). At its mouth, the river's estimated average discharge is 4,827 cubic feet per second (136.7 m3/s).

The Shiawassee River in the U.S. state of Michigan drains an area of 1,201 square miles (3,110 km2) within Oakland, Genesee, Livingston, Shiawassee, Midland and Saginaw counties. It flows in a generally northerly direction for approximately 110 miles (180 km) from its source to its confluence with the Tittabawassee River creating the Saginaw River, which drains into Saginaw Bay of Lake Huron.